Method for connecting semiconductor unit to object via bump

Abstract

The present invention provides methods for connecting, via at least a bump, at least a semiconductor unit to at least an object such as lead frame or substrate, which methods are characterized by comprising the steps of: forming at least an object bump on the object; contacting the object bump with a chip bump of the chip, with the melting points of the object bump and chip bump different from each other (specifically the melting point of the object bump is selected to be higher than that of the chip bump); and providing heat in such a way that the bump (specifically the chip bump) of lower melting point melts to flow along the surface of the object bump, and to let the object bump contact and connect the chip, resulting in the magnitude of the gap between the chip and the object being determined by the height of the object bump which has remained the same, leading to elimination of problems arising from the disunity of bumps' collapses inherent in conventional arts of connecting a chip to a lead frame or substrate via bumps.

What is claimed is:  
     
         1 . A method for connecting at least a semiconductor unit to at least an object via at least a bump wherein said semiconductor unit includes at least a bump of a first type, said method comprising the steps of: 
 forming at least a bump of a second type on said object wherein the melting point of the bump of said second type is higher than that of the bump of said first type;    arranging said semiconductor unit and said object in such a way that the bump of said first type and the bump of said second type face and contact each other; and    providing heat until the bump of said first type melts while the bump of said second type remains, the bump of said first type melts for the bump of said second type to contact and connect said semiconductor unit.    
     
     
         2 . The method according to  claim 1  wherein the bump of said first type is an alloy including more tin than lead while the bump of said second type is an alloy including more lead than tin.  
     
     
         3 . The method according to  claim 1  wherein the bump of said first type is an alloy of which 63 percentage is tin and 37 percentage is lead, while the bump of said second type is an alloy of which 90 percentage is lead and 10 percentage is tin.  
     
     
         4 . The method according to  claim 1  wherein the bump of said second type is formed by plating.  
     
     
         5 . The method according to  claim 1  wherein the step of providing heat is reflow soldering the bump of said first type.  
     
     
         6 . The method according to  claim 1  wherein said object is selected from among a substrate and a lead frame.  
     
     
         7 . The method according to  claim 1  wherein the bump of said first type and the bump of said second type contact each other in such a way that one is over the other.  
     
     
         8 . The method according to  claim 1  further comprising a step of applying 
 a force in such a way that the bump of said first type and the bump of said second type contact each other tightly with pressure.  
 
     
     
         9 . The method according to  claim 8  wherein the bump of said first type and the bump of said second type contact each other in such a way that one is over the other, and said force originates from gravity.  
     
     
         10 . The method according to  claim 1  further comprising a step of applying a force in such a way that the bump of said second type and said semiconductor unit tend to approach each other when the bump of said first type melts.  
     
     
         11 . The method according to  claim 1  wherein said heat is provided in such a way that the temperature of the bump of said first type reaches at least the melting point of the bump of said first type while the temperature of the bump of said second type remains below the melting point of the bump of said second type.  
     
     
         12 . The method according to  claim 1  wherein said heat is provided until the bump of said first type is fully melted and the bump of said second type contacts and connects said semiconductor unit.  
     
     
         13 . A method for connecting at least two semiconductor units to at least an object via bumps, wherein said semiconductor unit includes at least a bump of a first type and said object includes a first connection surface and a second connection surface, said method comprising the steps of: 
 forming, respectively on said first connection surface and said second surface, at least a bump of a second type, the melting point of the bump of said second type being higher than that of the bump of said first type;    arranging said semiconductor units and said object in such a way that the bump of said first type of each said semiconductor unit faces and contacts the bump of said second type on one of the connection surfaces of said object; and    providing heat in such a way that the temperature of the bump of said first type reaches a least the melting point of the bump of said first type while the temperature of the bump of said second type remains below the melting point of the bump of said second type, until the bump of said first type melts for the bump of said second type to contact and connect said semiconductor unit.    
     
     
         14 . The method according to  claim 13  wherein the bump of said second type is formed by plating.  
     
     
         15 . The method according to  claim 13  further comprising a step of applying a force in such a way that the bump of said first type and the bump of said second type contact each other with pressure.  
     
     
         16 . The method according to  claim 13  wherein said object is selected from among a substrate and a lead frame.  
     
     
         17 . The method according to  claim 16  further comprising a step of applying a force in such a way that the bump of said first type and the bump of said second type contact each other with pressure, said semiconductor units tend to respectively parallel said first connection surface and said second connection surface, and to approach said object when the bump of said first type melts.  
     
     
         18 . A method for connecting at least a semiconductor unit to at least an object via at least a bump, comprising the steps of: 
 forming at least an object bump on said object;    arranging said object, said semiconductor unit, and a connection medium in such a way that the connection medium is sandwiched between said object bump and said semiconductor unit, wherein the melting point of said connection medium is lower than that of said object bump and said semiconductor unit; and    providing heat in such a way that said connection medium melts while said object bump and said semiconductor unit remain, until said object bump contacts and connects said semiconductor unit.    
     
     
         19 . The method according to  claim 18  further comprising a step of applying a force in such a way that said semiconductor unit and said object bump, when said connection medium melts, approach each other until contact each other.